1. Field of the Invention
The present invention relates to an automobile independent suspension system, and specifically to technologies of automobile independent suspension systems which improve the driver feel, particularly a sensation created by the body roll during cornering by properly setting a ratio of a spring constant or a spring stiffness at each end of the vehicle on extension during rebound with respect to a spring constant at each end on compression during bound (or during jounce).
2. Description of the Prior Art
This type of suspension system for automobiles has been disclosed in Japanese Patent Provisional Publication No. 4-90911. The Japanese Patent Provisional Publication No. 4-90911 teaches the use of a higher bushing spring-constant (the stiffness of bushings incorporated in suspension arms) on extension during rebound in comparison with a bushing stiffness on compression during jounce. Thus, when the suspension moves into jounce and rebound and the movable end of the suspension arm with bushings swings, the bushes become softer on compression during bound and becomes harder on extension during rebound. Thus, during cornering, a rebound stroke of the inside suspension (or the inside suspension displacement in rebound) is less than a bound stroke of the outside suspension (or the outside suspension displacement in jounce). As a result of this, the body roll angle can be reduced effectively on turns. This improves the driver feel characteristics particularly roll feel characteristics. The use of bush having different bush stiffnesses on rebound and bound strokes, provides a simple and better suspension system, while allowing for slight assembly misalignment and at the same time achieving the anti-roll effect. The prior art suspension system is directed merely to the proper setting of the spring constant (the bush stiffness) of the bushing employed in the suspension arm on the jounce stroke and on the rebound stroke differently from each other. However, to more greatly enhance the driver feel (the roll feel) during cornering, it is desired to properly control roll-center-height characteristics as well as jack-up and jack-down characteristics (or jacking-force characteristic) whose jacking phenomenon is greatly affected by a bump-stop rubber serving as a nonlinear spring element.